Raw sewage smell at work only at certain times??

for the last 6 months or so we have had this raw sewage smell in the office at work, for some reason it only starts to smell after we have been there for a few hours. when we first come on its fine no odor.
but by 10.00 am its awful today people were vomiting, nausea, sore throat ,headaches, dizzy. my employer is doing nothing to remedy the problem and we need to know is this dangerous, should we even be breathing this stuff in??? help

There is no way that we can guess where your smell is coming from, or even if it is sewer gas at all.

If I had to be there, the first thing I would do is pour a bucket of water in any existing floor drains.
It is pretty common for the trap of a floor drain to dry out, and then the sewer gas has nothing to stop it from coming into the building.

Running water in the sinks is not the same as taking a cup, filling it up at the sink, and then finding the floor drains and pouring the water in them.
Whenever we plumbers "have" to work in offices, it's what we do. I don't understand why office workers put up with the smell of floor drains that have dried out.